Conventionally, a parallel type hybrid vehicle has both an engine and a motor/generator transmit driving forces to the automatic transmission at the time of starting, accelerating or the like. In such conventional hybrid vehicles the motor/generator functions as a generator in traveling downhill or braking, thereby supplementing the engine brake effect, and regenerating braking energy thereby improving fuel economy and reducing the amount of discharge of exhaust gas.
For example, as disclosed in U.S. Pat. No. 5,789,823, a motor/generator is arranged radially outward of a torque converter and the rotor of the motor/generator is integrally fixed to a small diameter portion of the torque converter.
However, in the above-described conventional structure, since the rotor is arranged radially outward of the torque converter, the position of the rotor changes as the torque converter is deformed by a centrifugal hydraulic pressure, a charge or the like, so that there is the risk that the rotor will interfere with the stator due to radial displacement of the rotor. Accordingly, in order to prevent interference between the stator and the rotor, it is necessary to determine the gap between the rotor and the stator in expectation of deformation of the torque converter. However, as the gap between the stator and the rotor is increased, efficiency of the motor is reduced. Further, axial positions of the stator and the rotor shift, whereby efficiency of the motor is reduced. Further, since the torque converter generates a lot of heat, when the torque converter and the rotor are integrally formed, heat is transmitted from the torque converter resulting in demagnetizing of the rotor. Further, if a lockup clutch and the rotor are arranged close to each other, dust such as iron powder or the like enter the lockup clutch from the rotor magnets, thereby preventing the lockup clutch from operating.
Accordingly, an object of the present invention is to provide a drive apparatus for a hybrid vehicle which does not reduce efficiency of the motor while reducing the overall axial dimension of the drive apparatus.